Regions
Northwest Inland.
Recent snowfall amounts vary significantly throughout the region. Areas that received less than 20 cm of new snow may see slightly lower avalanche hazard.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Tonight and Sunday: Periods of snow 5-15 cm. The freezing level is around 800-1000 m. Winds are strong easing to moderate from the W-SW. Monday: Cloudy with sunny breaks and possible flurries. The freezing level is around 1000 m. Winds are light but gusty from the W-SW. Tuesday: Periods of snow. The freezing level is around 1500 m and winds increase to strong from the SW.
Avalanche Summary
Reports suggest that a natural avalanche cycle most likely started overnight on Friday - at least in areas that received over 20 cm of new snow. Avalanches up to size 3 were expected. Most of these probably released on the recently buried snow surface, but some may have stepped down to the mid February layer.
Snowpack Summary
Up to 40 cm of dense storm snow now sits on a layer of surface hoar and/or a thick layer of facetted snow on shady slopes at all elevations, a sun crust on steep solar aspects, and various wind affected surfaces in exposed terrain. Strong southwest winds have created dense wind slabs on exposed lee slopes and in cross-loaded features. The early February weak layer of facets, crusts, and surface hoar is buried down about 50-100 cm. This layer could become reactive in the next couple days with additional loading and significantly warmer temperatures. Basal facets and depth hoar remain a concern in areas with thin or variable snow cover.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.